The disclosed embodiments are directed to improving efficiency and reliability of an electric machine and, more particularly, to improving cooling of rectifier electronics.
Alternators convert mechanical energy into electrical energy for a vehicle. The rotor of an automotive alternator is typically driven by a belt and pulley system to rotate within stator windings coiled on a laminated iron frame. The magnetic field from the spinning rotor induces an alternating voltage into the stator windings. The alternating voltage (AC) is typically then converted to a direct current (DC) voltage by a rectifying circuit that outputs the DC voltage to one or more batteries and to electrical devices of a vehicle.
A rectifying circuit may be formed using diodes, MOSFET devices, or by other structure. The rectifying circuit and associated control components may be located in an alternator housing.
Modern automotive alternators are generally required to supply ever-greater amounts of electrical current. For example, hybrid and electric vehicles may use electricity instead of internal combustion for driving the wheels, and an alternator may be combined with a starter in a mild hybrid configuration such as in a belt alternator starter (BAS) system. Other electrical loadings from air conditioning, electric power steering, and various vehicle systems further increase the required alternator electrical generation capacity. As a result, efficiency of automotive alternators needs to be optimized. Efficiency is generally limited by fan cooling loss, bearing loss, iron loss, copper loss, and the voltage drops in the rectifier bridges. The use of permanent magnets may increase efficiency by providing field flux without relying on a wound field that inherently creates ohmic losses. An alternator may have dual internal fans to improve operating efficiency and durability and to reduce heat-related failures. Many conventional alternator systems are addressed to such concerns. However, additional improvements are desirable.
Available space within a motor vehicle engine compartment is limited as manufacturers strive to reduce the size of vehicles while maximizing power and efficiency. With multiple components packed in a relatively small space, the heat generated by a number of devices increases the ambient temperature within the engine compartment. In addition, a tightly packed engine compartment may have limited space available for the flow of cooling air to reduce component temperatures. Excessive engine compartment temperatures may adversely affect alternator performance, including performance of individual components thereof.